1. Field of the Invention
The present invention relates to a method of manufacturing a magnetic head used for writing data on a recording medium and reading data stored on the recording medium, and a method of manufacturing a magnetic head substructure used in the method of manufacturing the magnetic head.
2. Description of the Related Art
For magnetic read/write devices such as magnetic disk drives, higher recording density has been constantly required to achieve a higher storage capacity and smaller dimensions. Typically, magnetic heads used in magnetic read/write devices are those having a structure in which a reproducing (read) head having a magnetoresistive element (that may be hereinafter called an MR element) for reading and a recording (write) head having an induction-type electromagnetic transducer for writing are stacked on a substrate.
For read heads, GMR (giant magnetoresistive) elements utilizing a giant magnetoresistive effect have been practically used as MR elements. Conventional GMR elements have a current-in-plane (CIP) structure in which a current used for detecting magnetic signals (that is hereinafter called a sense current) is fed in the direction parallel to the plane of each layer making up the GMR element. Recently, there has been proposed another type of GMR element having a current-perpendicular-to-plane (CPP) structure in which the sense current is fed in a direction intersecting the plane of each layer making up the GMR element, such as the direction perpendicular to the plane of each layer making up the GMR element. TMR elements utilizing a tunneling magnetoresistive effect are also known as another type of MR element. The TMR elements have a CPP structure, too. To achieve higher recording density of magnetic read/write devices, MR elements have been recently shifted from conventional GMR elements having the CIP structure to TMR elements or GMR elements having the CPP structure.
Write heads include those of a longitudinal magnetic recording system wherein signals are magnetized in the direction along the surface of the recording medium (the longitudinal direction) and those of a perpendicular magnetic recording system wherein signals are magnetized in the direction perpendicular to the surface of the recording medium. Recently, the shift from the longitudinal magnetic recording system to the perpendicular magnetic recording system has been promoted in order to achieve higher recording density of magnetic read/write devices.
In each of the longitudinal and perpendicular magnetic recording systems, the write head typically incorporates a coil for generating a magnetic field corresponding to data to be written on a recording medium, and a pole layer for allowing a magnetic flux corresponding to the magnetic field generated by the coil to pass therethrough and generating a write magnetic field for writing the data on the recording medium. The pole layer includes a track width defining portion and a wide portion, for example. The track width defining portion has a first end located in a medium facing surface and a second end located away from the medium facing surface, and has a width that defines the track width. The wide portion is coupled to the second end of the track width defining portion and has a width greater than the width of the track width defining portion. Here, the length of the track width defining portion taken in the direction orthogonal to the medium facing surface is called a neck height. The neck height exerts influences on write characteristics such as an overwrite property.
An example of a method of manufacturing a magnetic head will now be described. In the method, first, components of a plurality of magnetic heads are formed on a single substrate (wafer) to thereby fabricate a magnetic head substructure in which pre-head portions each of which will be the magnetic head later are aligned in a plurality of rows. The substructure includes a plurality of magnetoresistive films (hereinafter referred to as MR films) each of which will be formed into an MR element by undergoing lapping later. Each of the MR films has such a shape that the length taken in the direction orthogonal to the medium facing surface is greater than the length of the MR element and that the width is equal to the width of the MR element. Next, the substructure is cut into a plurality of head aggregates each of which includes a plurality of pre-head portions aligned in a row. Next, a surface formed in each of the head aggregates by cutting the substructure is lapped to thereby form the medium facing surface for each of the plurality of pre-head portions included in each of the head aggregates. At this time, each of the MR films is lapped, so that the length thereof reaches a predetermined length and the resistance thereof reaches a predetermined value, and as a result, the MR films are formed into the MR elements. Next, flying rails are formed on the medium facing surfaces. Next, each of the head aggregates is cut so that the plurality of pre-head portions are separated from one another, whereby a plurality of magnetic heads are formed.
An example of a method of forming the medium facing surface by lapping the head aggregate will now be described. In the method, a plurality of resistor layers are formed in advance on the substructure, each of the resistor layers having a resistance that changes with changing amount of lapping when the head aggregate is lapped later. The resistance of each of the resistor layers has a correspondence with the resistance of the MR element. When the head aggregate is lapped, lapping is performed while detecting the resistances of the plurality of resistor layers so that the resistance of each of the plurality of resistor layers is of a predetermined value. As a result, the medium facing surfaces are formed such that the resistance of each of the plurality of MR elements is equal to the target value thereof and that each of MR heights is equal to the target value thereof. The MR height is the length of the MR element taken in the direction orthogonal to the medium facing surface. Such a method of forming the medium facing surfaces as described above is disclosed in JP 11-134614A or JP 2005-317069A, for example.
JP 2006-048806A discloses a technique of optimizing both the throat height of the write head and the element height of the read head by performing processing of an air bearing surface using a processing detection pattern for controlling the throat height of the write head and a processing detection pattern for controlling the element height of the read head. JP 2006-048806A mentions that throat height here means length from the air bearing surface to the point (flare point) at which the width of the track width portion of the main pole begins to widen. The “throat height” mentioned in JP 2006-048806A therefore actually means neck height. The term “element height” appearing in JP 2006-048806A means the same as MR height, and the term “air bearing surface” appearing in JP 2006-048806A means the same as the medium facing surface.
In the conventional method of manufacturing a magnetic head, the substructure is fabricated such that there is a specific positional relationship between the MR film and the pole layer. Therefore, ideally, if the medium facing surfaces are formed such that each of the MR heights is of a specific value, uniform MR heights are thereby obtained.
If there is no variation in resistance-area product (RA) and width of the MR film among a plurality of substructures, it is possible to form MR elements through the above-described method of forming medium facing surfaces, such that the resistance of each of the MR elements is equal to the target value thereof and that each of the MR heights is equal to the target value thereof. In practice, however, there are some cases in which variations occur in resistance-area product and width of the MR film among a plurality of substructures. Even in such cases, it is possible to make the resistances of the MR elements uniform by performing lapping such that the resistance of each of the MR elements is equal to the target value. However, in the cases in which variations occur in resistance-area product and width of the MR film, if the MR elements are formed such that the resistances of the MR elements are uniform, there occur variations in MR height. In the case in which the MR film and the pole layer are formed to have a specific positional relationship with each other as previously described, if there occur variations in MR height, there occur variations in neck height, too.
Conventionally, in the case of write heads of the longitudinal magnetic recording system, when the recording density is low, variations in neck height do not exert great influences on write characteristics such as an overwrite property. However, as the recording density is increased, variations in neck height exert greater influences on write characteristics. In the case of write heads of the perpendicular magnetic recording system, variations in neck height exert greater influences on write characteristics, compared with write heads of the longitudinal magnetic recording system. Because of the foregoing, it has been required recently to reduce variations in neck height so as to obtain desired write characteristics.
The technique disclosed in JP 2006-048806A allows optimization of both the neck height and the throat height. According to this technique, however, the following problems are encountered when variations occur in resistance-area product and width of the MR films as mentioned above. First, in the case where the MR elements are formed such that the MR heights are uniform, there occurs a problem that the resistances of the MR elements vary in response to the variations in resistance-area product and width of the MR films. On the other hand, in the case where the MR elements are formed such that the resistances of the MR elements are uniform, the MR heights vary in response to the variations in resistance-area product and width of the MR films. In this case, since the MR heights vary while the neck heights are uniform, there occurs variations in angle formed by the medium facing surface with respect to the top surface of the substrate. The technique disclosed in JP 2006-048806A further has a disadvantage that the processing on the air bearing surface is complicated because it requires use of both the detection pattern disposed at a height corresponding to the read head and the detection pattern disposed at a height corresponding to the write head.